CHAPTER 3 Preparation for Awake Intubation Ian R. Morris 3.2.2 The nose 3.1 INTRODUCTION Anatomically, the nose can be divided into an external component and the nasal cavity.4 The external nose consists of a bony vault 3.1.1 What are the fundamentals of an posterior superiorly, a cartilaginous vault anteriorly, and the lobule awake, bronchoscopically facilitated at the inferior-anterior aspect (see Figure 3-2).3 The cavity of the intubation? nose is divided into bilateral compartments by the nasal septum and continues posteriorly from the nostrils (nares), to communi- Awake bronchoscopic intubation, if it is to be performed rapidly and cate with the nasopharynx at the posterior aspect of the septum (the with minimal patient discomfort, requires an in-depth knowledge choanae) (see Figures 3-3 to 3-5).3 The nasal vestibule is a small of the anatomy of the airway, adequate regional anesthesia, and dilatation located immediately inside the nostrils.3,4 Each nasal dexterity with bronchoscopic manipulation. In order to achieve cavity is bounded by a floor, a roof, and medial and lateral walls.3-5 optimal regional anesthesia of the airway and avoid complications, The roof of the nasal cavity extends posteriorly from the bridge of a thorough knowledge of the local anesthetics employed and tech- the nose, and consists of the lateral nasal cartilages, the nasal bones niques of administration is necessary. The primary requirement and spine of the frontal bone, the cribriform plate of the eth- for successful awake intubation is effective regional anesthesia of moid, and the inferior aspect of the sphenoid (see Figure 3-2).3,4,6 the airway.1 The nasal septum forms the medial wall, and is formed by the quadrilateral cartilage, the perpendicular plate of the ethmoid, and the vomer (see Figure 3-5).3 The lateral wall is formed anterior- 3.2 AIRWAY ANATOMY inferiorly by the frontal process of the maxilla, the nasal bones anterior-superiorly, the nasal aspect of the ethmoid superiorly, and the perpendicular plate of the palatine and medial pterygoid 3.2.1 Why is knowledge of upper airway plate posteriorly.3,7 A series of three horizontal scroll-like ridges anatomy beneficial in airway (conchae or turbinates) project medially from the lateral walls management? of the nasal cavities, each of which overhangs a corresponding groove or meatus (see Figures 3-2 to 3-4).3,8 Septal deviation is Knowledge of the structure, function, and pathophysiology of the common, may be associated with compensatory hypertrophy of upper airway permits the practitioner to anticipate potential life- the turbinates, and can produce nasal obstruction.3,4 The parana- threatening problems and better utilize the full spectrum of airway sal sinuses and the nasolacrimal duct empty into the nasal cavity management techniques.2 Functionally, the upper airway can be through ostia in the lateral wall.3 Obstruction of the ostia of the considered to consist of the nasal cavities, pharynx, larynx, and tra- paranasal sinuses can occur with prolonged nasal intubation and chea (see Figure 3-1).3 The oral cavity provides an alternate access can cause sinusitis.2,3 The floor of each nasal cavity is concave and route to the pharynx. is formed by the palatine process of the maxilla and the horizontal 30 HUNG_PT1_Ch03_030-067.indd 30 8/23/11 2:53:53 PM CHAPTER 3 • Preparation for Awake Intubation 31 FIGURE 3-1. Sagittal view of the upper airway. FIGURE 3-2. Bony components of lateral nasal wall. HUNG_PT1_Ch03_030-067.indd 31 8/23/11 2:54:00 PM 32 SECTION 1 • Foundations of Difficult and Failed Airway Management Crista galli Ethmoidal air cells Superior turbinate Middle Orbit turbinate Inferior turbinate Antral ostium ETT Maxillary Nasal antrum Hard palate septum (maxilla) FIGURE 3-3. Coronal section of the maxillary sinus. The position of a nasotracheal tube (ETT) is shown in the right nasal cavity. FIGURE 3-4. Lateral nasal wall. FIGURE 3-5. Medial nasal wall. HUNG_PT1_Ch03_030-067.indd 32 8/23/11 2:54:06 PM CHAPTER 3 • Preparation for Awake Intubation 33 plate of the palatine bone.3,4 The floor extends posteriorly in a the posterior-inferior aspect.3,9 The vestibule receives blood supply transverse plane from the vestibule. from both the anterior ethmoidal and sphenopalatine arteries as The major nasal airway is located below the inferior turbinate, well as from nasal branches of the superior labial branch of the declines slightly front to back (approximately 20 degrees), and facial artery (see Figures 3-6 A and B).3,9 Anastomoses between a nasotracheal tube or flexible endoscope should be directed vessels from these three different sources occur particularly at the backward and slightly inferiorly along the floor of the nose.2-4 anterior-inferior aspect of the septum (Little’s area or Kiesselbach’s Occasionally, the posterior aspect of the inferior turbinate may plexus), and this is a common site of epistaxis.3,4,9 Tintinalli be hypertrophied and resistance to the passage of a nasotracheal reported moderate to severe epistaxis in 7% of 71 attempted emer- tube may be encountered at this location.4 Alternating counter- gency nasotracheal intubations.10 The single case of severe epistaxis clockwise/clockwise rotation of the tube changes the orientation in this series occurred in a patient with cirrhosis. Minimal epistaxis of the bevel and may facilitate negotiation of the nasal cavity (see has been reported in 11% to 40% of nasal intubations.10,11 In Chapter 11). a series of 99 patients undergoing nasotracheal intubation for The anterior and posterior ethmoidal branches of the internal oromaxillofacial surgery, epistaxis occurred in 6 patients but carotid artery supply the anterior-superior aspect of the nasal cav- was sufficient to result in a visible accumulation of blood in the ity and the sphenopalatine branch of the external carotid supplies pharynx in only 1 patient.12 Of 175 anesthetists who underwent FIGURE 3-6. (A and B.) Blood supply to mucosa of lateral nasal wall and septum. HUNG_PT1_Ch03_030-067.indd 33 8/23/11 2:54:10 PM 34 SECTION 1 • Foundations of Difficult and Failed Airway Management FIGURE 3-7. (A and B.) Nerve supply to mucosa of the lateral nasal wall and nasal septum. nasotracheal intubation at a training course, minor nasal bleeding aspect by the posterolateral nasal branches of the sphenopalatine was seen in 20 during endoscopy or after extubation.13 None of nerve.3,4,9 Anteriorly, the floor of the nose is supplied by the the 20 subjects required suction to control bleeding or clear the anterior-superior dental branch of the infraorbital nerve and pos- airway, and the bleeding did not interfere with endoscopy. During teriorly by the greater palatine.3,4 Rootlets of the olfactory nerve nasal intubation passing the tube with the bevel at the tip facing located in the roof of the nose adjacent to the cribriform plate the septum directs the leading edge away from the vascular septum; transmit the sense of smell.3 however, the optimum orientation of the tube is controversial (see In addition to being a respiratory pathway, the nose humidifies Blind Nasal Intubation section in Chapter 11).14 Perforation into and warms inspired air, houses the olfactory receptors, removes the submucosal space can occur and lead to hematoma and abscess bacteria, dust, and other particles from inspired air, and acts as a formation in the retropharyngeal space.2,3 Excessive force must be voice resonator.3,4,8 avoided.3 Common sensation to the nasal cavities is supplied by the 3.2.3 The mouth ophthalmic and maxillary divisions of the trigeminal nerve.2,3 The posterior aspect of the septum is innervated by the short Anatomically, the mouth consists of (1) the vestibule which is and long sphenopalatine branches of the maxillary nerve.3,4 bounded externally by the lips and cheeks and internally by the gums Anteriorly the septum and the lateral wall is supplied by the and teeth and (2) the mouth cavity.3,4 The mouth cavity is bounded anterior ethmoidal branch of the ophthalmic nerve (see Figures 3-7A by the alveolar arches and the teeth anteriorly and laterally, the and B).7 The posterior-superior aspect of the lateral wall is hard palate and the anterior aspect of the soft palate above, and the innervated by the short sphenopalatine nerve and the inferior anterior two-thirds of the tongue and the reflection of its mucosa HUNG_PT1_Ch03_030-067.indd 34 8/23/11 2:54:13 PM CHAPTER 3 • Preparation for Awake Intubation 35 onto the floor of the mouth and mandible below.3,4 Posteriorly, the oral cavity opens into the oropharynx at the oropharyngeal Nerve V isthmus.3-5 The anterior two-thirds of the palate (hard palate) is composed of the palatine plates of the maxillae and the horizontal plates of the palatine bones (see Figure 3-2).3,4,15 Posteriorly the hard palate is continuous with the soft palate, which is composed of a tough, fibrous sheath and extends to a free posterior border. In the midline, the soft palate ends in the uvula3,4,15 then curves laterally to blend into the lateral pharyngeal wall at the palatoglos- sal and palatopharyngeal folds (anterior and posterior tonsillar pil- Nerve lars), respectively.3,4,15 The anterior and inferior aspect of the soft IX palate faces the mouth cavity and oropharynx, whereas the poste- rior and superior aspect is part of the nasopharynx.3,4,15 The uvula is a valuable midline landmark during bronchoscopic intubation through the mouth. Movement of the soft palate is controlled by Nerve X five paired muscles including palatoglossus and palatopharyngeus, which descend in their respective folds to blend with the side of the tongue (palatoglossus) and the side wall of the pharynx FIGURE 3-8.